Cap-less writing instruments having a writing member which is prevented from drying can be roughly classified into two groups: in the first group, the writing member is prevented from drying by improving the ink or the air hole, and in the second group, a drying preventing mechanism is provided in the writing instrument body. Examples of the writing instrument of the first group are a marking-pen using so-called "non-dry ink", and a ball-point pen using aqueous ink which is difficult to dry and which has a very small air hole at the rear end of the writing member. These types of writing instruments do not have a drying preventing mechanism, and therefore, the writing member is not sufficiently protected from drying. Accordingly, before the writing instrument is presented on the market, the writing member must be wrapped with aluminum foil or the like separately from the writing instrument body. Examples of the writing instrument of the second group are a rotary type writing instrument and a click (retractable) type writing instrument. These writing instruments are intricate in construction and consist of a large number of components and accordingly have high manufacturing costs. Furthermore, these writing instruments are not so sufficiently sealed and therefore cannot be placed on sale with the writing member accommodated in the writing instrument body. Accordingly, a person cannot test the writing instrument before he buys it.
On the other hand, writing instruments which are simple in construction and sufficiently sealed have been proposed in the art. However, these writing instruments are disadvantageous in that, when used, the body has to be maintained substantially horizontal for extracting the writing member and a tip end of the writing member has to be maintained downward for retracting the writing member into the body. In other words, these types of writing instruments require intricate directional operation. Further, they have an unsatisfactory design.